This invention relates to a process for producing 5-methyl-N-aryl-2-pyrrolidone and 5-methyl-N-cycloalkyl-2-pyrrolidone by reductive amination of levulinic acid or its derivatives amine salts with aryl amines, ammonia or ammonium hydroxide utilizing a metal catalyst, which is optionally supported.
Levulinic acid is a well-known product of hexose acid hydrolysis, and can be inexpensively obtained from cellulose feedstocks. Consequently, it is an attractive starting material in producing many useful 5-carbon compounds and their derivatives. For example, N-cyclohexyl-2-pyrrolidone is used as a solvent or intermediate in many industrial applications, including the electronics industry (photo-resist stripping solutions), industrial cleaners, oil gas well maintenance, and fiber dyeing.
U.S. Pat. No. 3,337,585 discloses a process for preparing 5-methyl-1-alkyl-2-pyrrolidone utilizing levulinic acid and a primary alkyl amine at a temperature of 50xc2x0 C. to 350xc2x0 C. under carbon monoxide at a pressure of 1.0 to 101 MPa. Additional potential primary amines include alkylene diamines, aryl amines and cycloalkyl amines. In U.S. Pat. No. 3,235,562 a vapor phase process is used for the production of lactams by reductive amination of oxo carboxylic acid compounds. Alkyl or aryl volatile primary amines may be used. Candeloro and Bowie (Aust. J. Chem., 1978, 31:2031-2037) describe a process for producing 5-methyl-2,3-dihydro-1-H-benzazepin-2-one and 5-(2-methyl-5-oxo-1-phenylpyrrolidin-2-yl)-4-oxo-N-phenylpentanamide by reacting levulinic acid with aniline under a nitrogen atmosphere.
An efficient and low cost process for the production of aryl, alkyl and cycloalkyl pyrrolidones would be advantageous.
The present invention is a novel, one-step process for converting levulinic acid or its amine salts and aryl amines, ammonia or ammonium hydroxide to aryl and cycloalkyl pyrrolidones as set forth in greater detail below in the presence of catalysts. Specifically, the present invention relates to a process for preparing 5-methyl-N-aryl-2-pyrrolidone (III), 5-methyl-N-cycloalkyl-2-pyrrolidone (IV), or a mixture thereof, which comprises the step of contacting the compound levulinic acid (I) with an aryl amine (II) in the presence of a catalyst and hydrogen gas; 
wherein R1 is an aromatic group having from 6 to 30 carbons and R2 is a fully or partially reduced derivative of R1, and wherein 5-methyl-N-aryl-2-pyrrolidone (III), 5-methyl-N-cycloalkyl-2-pyrrolidone (IV), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
The catalyst useful in the process of the invention is selected from metals from the group consisting of palladium, ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt, copper, iron, osmium; compounds thereof; and combinations thereof.
The present invention also relates to a process for preparing 5-methyl-N-aryl-2-pyrrolidone (VII), 5-methyl-N-cycloalkyl-2-pyrrolidone (VIII), or a mixture thereof, which comprises the step of contacting an ammonium salt of levulinic acid (V) with an aryl amine (VI) in the presence of a catalyst and hydrogen gas; 
wherein R1 is an aromatic group having from 6 to 30 carbons and R2 is a fully or partially reduced derivative of R1, and wherein 5-methyl-N-aryl-2-pyrrolidone (VII), 5-methyl-N-cycloalkyl-2-pyrrolidone (VIII), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
The catalyst useful in this process of the invention is selected from metals from the group consisting of palladium, ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt, copper, iron, osmium; compounds thereof; and combinations thereof.
The present invention also relates to a process for preparing 5-methyl-N-aryl-2-pyrrolidone (XI), 5-methyl-N-cycloalkyl-2-pyrrolidone (XII), or a mixture thereof, which comprises the step of contacting an R3-ammonium salt of levulinic acid (IX) with ammonia or ammonium hydroxide (X) in the presence of a catalyst and hydrogen gas; 
wherein R3 is an aromatic group having from 6 to 30 carbons, R2 is a fully or partially reduced derivative of R3, and A is hydrogen or hydronium ion (H3O+), and wherein 5-methyl-N-aryl-2-pyrrolidone (XI), 5-methyl-N-cycloalkyl-2-pyrrolidone (XII), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
The catalyst useful in this process of the invention is selected from metals from the group consisting of palladium, ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt copper, iron, osmium; compounds thereof; and combinations thereof.
By xe2x80x9clevulinic acidxe2x80x9d is meant the compound having the following formula: 
By xe2x80x9cR3-ammonium salt of levulinic acidxe2x80x9d is meant the compound having the following formula wherein R3 is an aromatic group having from 6 to 30 carbons: 
By xe2x80x9caryl aminexe2x80x9d is meant the compound having the formula Rxe2x80x94NH2 wherein R is an aromatic group. An xe2x80x9caromatic groupxe2x80x9d is benzene or compounds that resemble benzene in chemical behavior.
By xe2x80x9c5-methyl-N-aryl-2-pyrrolidonexe2x80x9d is meant the compound having the general formula below wherein R1 is an aryl group having from 6 to 30 carbons: 
By xe2x80x9c5-methyl-N-cycloalkyl-2-pyrrolidonexe2x80x9d is meant the compound having the general formula below wherein R2 is a cycloalkyl group having from 6 to 30 carbons: 
By xe2x80x9ccatalystxe2x80x9d is meant a substance that affects the rate of the reaction but not the reaction equilibrium, and emerges from the process chemically unchanged.
By xe2x80x9cmetal catalystxe2x80x9d is meant a catalyst that is comprised of at least one metal, at least one Raney metal, compounds thereof or combinations thereof.
By xe2x80x9cpromoterxe2x80x9d is meant an element of the Periodic Table that is added to enhance the physical or chemical function of the catalyst. The promoter can also be added to retard undesirable side reactions and/or affect the rate of the reaction.
By xe2x80x9cmetal promoterxe2x80x9d is meant a metallic compound that is added to enhance the physical or chemical function of a catalyst. The metal promoter can also be added to retard undesirable side reactions and/or affect the rate of the reaction.
By xe2x80x9cfully or partially reduced derivativexe2x80x9d of an aryl compound is meant a compound that can be derived from the parent compound by saturating or reducing one or more of the unsaturated bonds in the aromatic ring. Unsaturated compounds are compounds that contain one or more carbon to carbon double or triple bonds. For example, a fully reduced derivative of a phenyl group is a cyclohexyl group.
This invention relates to the synthesis of 5-methyl-N-aryl-2-pyrrolidone (III), 5-methyl-N-cycloalkyl-2-pyrrolidone (IV) or a mixture thereof, from a reaction between levulinic acid (I) and an aryl amine (II) in the presence of a catalyst and hydrogen gas; 
wherein R1 is an aromatic group having from 6 to 30 carbons and R2 is a fully or partially reduced derivative of R1, and wherein 5-methyl-N-aryl-2-pyrrolidone (III), 5-methyl-N-cycloalkyl-2-pyrrolidone (IV), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
In addition, this invention relates to the synthesis of 5-methyl-N-aryl-2-pyrrolidone (VII), 5-methyl-N-cycloalkyl-2-pyrrolidone (VIII) or a mixture thereof, from a reaction between an ammonium salt of levulinic acid (V) and an aryl amine (VI) in the presence of a catalyst and hydrogen gas; 
wherein R1 is an aromatic group having from 6 to 30 carbons and R2 is a fully or partially reduced derivative of R1, and wherein 5-methyl-N-aryl-2-pyrrolidone (VII), 5-methyl-N-cycloalkyl-2-pyrrolidone (VIII), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
In addition, this invention relates to the synthesis of 5-methyl-N-aryl-2-pyrrolidone (XI), 5-methyl-N-cycloalkyl-2-pyrrolidone (XII) or a mixture thereof, from a reaction between an R3-ammonium salt of levulinic acid (IX) and ammonia or ammonium hydroxide (X) in the presence of a catalyst and hydrogen gas; 
wherein R3 is an aromatic group having from 6 to 30 carbons, R2 is a fully or partially reduced derivative of R3, and A is hydrogen or hydronium ion (H3O+), and wherein 5-methyl-N-aryl-2-pyrrolidone (XI), 5-methyl-N-cycloalkyl-2-pyrrolidone (XII), or a mixture thereof, may comprise 100% by weight of the total products formed, or wherein additional products may be produced.
A catalyst, with or without a support, may be present in the processes of the invention to effect the amination reactions. A promoter may optionally be used to aid the reactions. The promoter can be a metal.
The processes of the present invention may be carried out in batch, sequential batch (i.e., a series of batch reactors) or in continuous mode in any of the equipment customarily employed for continuous process (see for example, H. S. Fogler, Elementary Chemical Reaction Engineering, Prentice-Hall, Inc., N.J., USA). The condensate water formed as the product of the reaction is removed by separation methods customarily employed for such separations, such as distillation.
The aryl and cycloalkyl groups represented by R1, R2 and R3 preferably have from 6 to 30 carbons. More preferably, the aryl and cycloalkyl groups have from 6 to 12 carbons. Examples of preferred embodiments of Formula (II) or Formula (VI) include aniline and toluidine.
In the processes of the invention, a molar ratio of aryl amine to levulinic acid, the ammonium salt of levulinic acid or the R3-ammonium salt of levulinic acid of from about 0.01/1 to about 100/1, is preferred at the start of the reaction. A molar ratio of from about 0.4/1 to about 5/1 is further preferred. Similarly, a molar ratio of ammonia or ammonium hydroxide to the R3-ammonium salt of levulinic acid of from about 0.01/1 to about 100/1, is preferred at the start of the reaction. A molar ratio of ammonia or ammonium hydroxide to the R3-ammonium salt of levulinic acid of from about 0.4/1 to about 5/1 is further preferred.
A temperature range of from about 50xc2x0 C. to about 300xc2x0 C. is preferred for the processes of the invention. A temperature range of from about 75xc2x0 C. to about 200xc2x0 C. is further preferred.
A pressure range of from about 0.3 MPa to about 20 MPa is employed for the processes of the invention. A pressure range of from about 1.3 MPa to about 7.6 MPa is preferred.
The reactions of the present invention can be performed in non-reacting solvent media such as water, alcohols, ethers, and pyrrolidones. Alternatively, the excess of aryl amine can also act as the solvent medium.
The catalyst useful in the invention is a substance that affects the rate of the reaction but not the reaction equilibrium, and emerges from the process chemically unchanged. A chemical promoter generally augments the activity of a catalyst. The promoter herein may be incorporated into the catalyst during any step in the chemical processing of the catalyst constituent. The chemical promoter generally enhances the physical or chemical function of the catalyst agent, but can also be added to retard undesirable side reactions.
The processes of the invention involve reductive amination of levulinic acid or its amine salts with an aryl amine, ammonia or ammonium hydroxide, which is effected in the presence of a catalyst. The principal component of the catalyst useful herein is selected from metals from the group consisting of palladium, ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt, copper, iron, osmium; compounds thereof; and combinations thereof.
A promoter may be used optionally in the reactions of the present invention. The promoter herein may be incorporated into the catalyst during any step in the chemical processing of the catalyst constituent. Suitable promoters for the processes of the invention include metals selected from tin, zinc, copper, gold, silver, and combinations thereof. The preferred metal promoter is tin. Other promoters that can be used are elements selected from Group 1 and Group 2 of the Periodic Table.
The catalyst used in the process may be supported or unsupported. A supported catalyst is one in which the active catalyst agent is deposited on a support material by a number of methods, such as spraying, soaking or physical mixing, followed by drying, calcination, and if necessary, activation through methods such as reduction or oxidation. Materials frequently used as a support are porous solids with high total surface areas (external and internal) which can provide high concentrations of active sites per unit weight of catalyst. The catalyst support may enhance the function of the catalyst agent. A supported metal catalyst is a supported catalyst in which the catalyst agent is a metal.
A catalyst that is not supported on a catalyst support material is an unsupported catalyst. An unsupported catalyst may be platinum black or a Raney catalyst. The term xe2x80x9cRaney catalystxe2x80x9d as used herein refers to catalysts that have a high surface area due to selectively leaching an alloy containing the active metal(s) and a leachable metal (usually aluminum). The term Raney catalyst is not meant to denote any particular source of the material. Raney catalysts have high activity due to the higher specific area and allow the use of lower temperatures in hydrogenation reactions. The active metals of Raney catalysts include nickel, copper, cobalt, iron, rhodium, ruthenium, rhenium, osmium, iridium, platinum, palladium; compounds thereof; and combinations thereof.
Promoter metals may also be added to the base Raney metals to affect selectivity and/or activity of the Raney catalyst. Promoter metals for Raney catalysts may be selected from transition metals from Groups IIIA through VIIIA, IB and IIB of the Periodic Table of the Elements. Examples of promoter metals include chromium, molybdenum, platinum, rhodium, ruthenium, osmium, and palladium, typically at about 2% by weight of the total metal.
The catalyst support useful herein can be any solid, inert substance including, but not limited to, oxides such as silica, alumina and titania; barium sulfate; calcium carbonate; and carbons. The catalyst support can be in the form of powder, granules, pellets, or the like.
A preferred support material of the invention is selected from the group consisting of carbon, alumina, silica, silica-alumina, silica-titania, titania, titania-alumina, barium sulfate, calcium carbonate, strontium carbonate, compounds thereof and combinations thereof. Supported metal catalysts can also have supporting materials made from one or more compounds. More preferred supports are alumina, carbon and titania. Further preferred supports are carbons with a surface area greater than 100 m2/g. A further preferred support is carbon with a surface area greater than 200 m2/g. Preferably, the carbon has an ash content that is less than 5% by weight of the catalyst support; the ash content is the inorganic residue (expressed as a percentage of the original weight of the carbon) which remains after incineration of the carbon.
Commercially available carbons which may be used in this invention include those sold under the following trademarks: Bameby and Sutcliffe(trademark), Darco(trademark), Nuchar(trademark), Columbia JXN(trademark), Columbia LCK(trademark), Calgon PCB(trademark), Calgon BPL(trademark), Westvaco(trademark), Norit(trademark) and Bamaby Cheny NB(trademark). The carbon can also be commercially available carbon such as Calsicat C, Sibunit C, or Calgon C (commercially available under the registered trademark Centaur(R)).
In the processes of the invention, the preferred content of the metal catalyst in the supported catalyst is from about 0.1% to about 20% of the supported catalyst based on metal catalyst weight plus the support weight. A more preferred metal catalyst content range is from about 1% to about 10% of the supported catalyst. A further preferred metal catalyst content range is from about 3% to about 7% of the supported catalyst.
Combinations of catalyst and support system may include any one of the metals referred to herein with any of the supports referred to herein. Preferred combinations of catalyst and support include palladium on carbon, palladium on calcium carbonate, palladium on barium sulfate, palladium on alumina, palladium on titania, palladium on silica, platinum on carbon, platinum on alumina, platinum on silica, iridium on silica, iridium on carbon, iridium on alumina, rhodium on carbon, rhodium on silica, rhodium on alumina, nickel on carbon, nickel on alumina, rhenium on carbon, rhenium on silica, rhenium on alumina, ruthenium on carbon, ruthenium on alumina, ruthenium on silica and combinations thereof.
Further preferred combinations of catalyst and support include palladium on carbon, palladium on alumina, palladium on titania, platinum on carbon, platinum on alumina, rhodium on carbon, rhodium on alumina and combinations thereof.
The levulinic acid useful in the processes of the invention may be obtained using traditional chemical routes or obtained from biobased, renewable cellulosic feedstocks. Utilization of bio-derived levulinic acid is likely to reduce the cost of manufacture of the compounds herein relative to conventional methods.
The compounds produced by the processes of the invention display properties that are useful in diverse applications. N-alkyl pyrrolidones with alkyl chains up to about 8 carbons function as aprotic chemical solvents with a lower toxicity profile than other solvents. The carbon chains of N-lower pyrrolidones are not long enough to allow micelle formation in water; thus these compounds do not exhibit significant surfactant properties. N-alkyl pyrrolidones with alkyl groups of about C8 to C14 exhibit surfactant properties, and pyrrolidones with longer N-alkyl chains act as complexing agents. The surface active properties of alkyl pyrrolidones, such as solubility, wetting, viscosity building, emulsifying and complexing are described in U.S. Pat. No. 5,294,644. N-alkyl pyrrolidones can also be used for concentrating colloidal particles. Due to their solvent, surfactant and complexing properties, pyrrolidones are very useful in the manufacture of pharmaceuticals, personal care products, and industrial, agricultural and household chemicals and products.
The pyrrolidones produced by the processes of the invention are useful in preparing pharmaceutical products for use on humans, animals, reptiles, and fish. The pyrrolidones disclosed herein are particularly useful in topical formulations, such as ointments, creams, lotions, pastes, gels, sprays, aerosols, lotions, shampoos, foams, creams, gels, ointments, salves, milks, sticks, sprays, balms, emulsions, powders, solid or liquid soaps, or oils. Pyrrolidones, such as 5-methyl-2-pyrrolidones, can be used to enhance the transdermal penetration of active components into human or animal tissues and systems. Pyrrolidones can also act as solubilizers to enhance the solubility of a therapeutic agent in the carrier system.
The pyrrolidones produced by the processes of the invention may also be incorporated into matrix systems, such as patches, for the transdermal administration of, for example, an antimicrobial, a hormone, or an anti-inflammatory. The methods of preparation of pharmaceutical compositions as are commonly practiced in the pharmaceutical industry are useful with the processes of the invention. For discussion of such methods, see, for example, Remington""s Pharmaceutical Sciences (AR Gennaro, ed., 20th Edition, 2000, Williams and Wilkins, PA) incorporated herein by reference.
The pyrrolidones made by the processes of the invention may be used as solvents or surfactants in liquid, gel or aerosol cleaning compositions for cleaning a wide range of surfaces, including textiles, such as clothing, fabrics and carpets, and hard surfaces, such as glass, metal, ceramics, porcelain, synthetic plastics and vitreous enamel. The pyrrolidones may also be used in formulations for disinfecting hard surfaces, such as in the household, or in institutional or hospital environments, or the surface of skin, or fabric surfaces, or in the food preparation, restaurant or hotel industries. In addition, cleaning compositions are useful for the removal of industrial soils, such as dirt, grease, oil, ink and the like. The pyrrolidones may also be used as solvents in compositions for cleaning, solvating, and/or removing plastic resins or polymers from manufactured articles or manufacturing equipment.
In addition to pyrrolidones, other components may be included in cleaning compositions. These additional components include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and solvents. Illustrative nonionic surfactants are alkyl polyglycosides, such as Glucopon (Henkel Corporation), ethylene oxide and mixed ethylene oxide/propylene oxide adducts of alkylphenols, the ethylene oxide and mixed ethylene oxide/propylene oxide adducts of long chain alcohols or of fatty acids, mixed ethylene oxide/propylene oxide block copolymers, esters of fatty acids and hydrophilic alcohols, such as sorbitan monooleate, alkanolamides, and the like.
Illustrative anionic surfactants are the soaps, higher alkylbenzene sulfonates containing from 9 to 16 carbons in the higher alkyl group in a straight or branched chain, C8-C15 alkyl toluene sulfonates, C8-C15 alkyl phenol sulfonates, olefin sulfonates, paraffin sulfonates, alcohol and alcoholether sulfates, phosphate esters, and the like.
Illustrative cationic surfactants include amines, amine oxides, alkylamine ethoxylates, ethylenediamine alkoxylates such as the Tetronic(copyright) series from BASF Corporation, quaternary ammonium salts, and the like.
Illustrative amphoteric surfactants are those which have both acidic and basic groups in their structure, such as amino and carboxyl radicals or amino and sulfonic radicals, or amine oxides and the like. Suitable amphoteric surfactants include betaines, sulfobetaines, imidazolines, and the like.
Illustrative solvents include glycols, glycol ethers, aliphatic alcohols, alkanolamines, pyrrolidones and water.
Such surfactants and solvents are described, for example, in McCutcheon""s (2002), Volume 1 (Emulsifiers and Detergents) and Volume 2 (Functional Materials), The Manufacturing Confectioner Publishing Co., Glen Rock, N.J.
Cleaning compositions may also include additional components, such as chelating agents, corrosion inhibitors, antimicrobial compounds, buffering and pH adjusting agents, fragrances or perfumes, dyes, enzymes and bleaching agents.
N-alkyl-2-pyrrolidones are useful in cleaning and stripping formulations which are used to remove (or strip) a photoresist film (or other similar organic polymeric material film) or layer from a substrate, or to remove or clean various types of plasma-etch residues from a substrate. N-alkyl-2-pyrrolidones are also useful as surfactants in cleaning formulations for removing solder pastes from printing applicators and circuit assemblies.
N-alkyl-2-pyrrolidones, such as 5-methyl-N-octyl-2-pyrrolidone and 5-methyl-N-dodecyl-2-pyrrolidone, may be included as components in ink jet inks in order to improve resistance to highlighter smear when printed into an image, lead to an even print (minimize the degree of banding) and impart an improved waterfast resistance and/or a better dry or wet rub property. 2-Pyrrolidones, such as 5-methyl-N-cyclohexyl-2-pyrrolidone or 5-methyl-N-methyl-2-pyrrolidone, may also be used as a solvent in the preparation of hot melt or phase change inks for color printing.
The pyrrolidones made by the processes of the invention can also be utilized in the manufacture of agrochemicals, including but not limited to herbicides, insecticides, fungicides, bactericides, nematicides, algicides, mulluscicides, virucides, compounds inducing resistance to plants, repellants of birds, animals and insects, and plant growth regulators, or mixtures thereof. The method of manufacture comprises contacting an agrochemically effective agent as known to persons""skilled in the art with at least one of the pyrrolidones produced by any of the methods of the invention. The agrochemical composition can optionally comprise additional auxilary components as are commonly used in the agrochemical industry.
Pyrrolidones, such as 5-methyl-N-methyl pyrrolidone and 5-methyl-N-cyclohexyl pyrrolidone, can be used as water insoluble polar co-solvents to solubilize water insoluble pesticides and other agrochemicals and increase the effective amount of active ingredient. N-alkyl pyrrolidones, preferably Nxe2x80x94C3-15 alkyl pyrrolidones, in particular 5-methyl-N-octyl pyrrolidone and 5-methyl-N-dodecylpyrrolidone, can be used as nonionic surfactants that aid as emulsifiers. Plant growth regulators are used to improve the economic yield of agricultural plants. 5-Methyl-N-octyl pyrrolidone and 5-methyl-N-dodecyl pyrrolidone can be utilized as solvents in emulsions containing plant growth regulators.
In addition, pyrrolidones can be utilized in liquid or aerosol formulations for dermal application of insect repellants by humans; examples include mosquito and tick repellants. Manufacture of such insect repellants comprises contacting an effective amount of at least one insect repelling agent with at least one product produced using at least one process of the invention.
Pyrrolidones, such as 5-methyl-N-methyl-2-pyrrolidone, can also be used in antimicrobial formulations for the preservation of animal silage.
5-Methyl-N-alkyl-2-pyrrolidones can also be used as part of a more environmentally-conscious method for dry-cleaning clothing that includes a surfactant and densified carbon dioxide in place of traditional solvents.
In addition, 5-methyl-2-pyrrolidones can be used as components in a protective composition for use on painted surfaces, such as cars. The pyrrolidones function to wet the surface and promote spreadability of the protectant.
Different plastic materials are often not miscible, resulting in products that exhibit insufficient mechanical properties. Monomeric and polymeric 5-methyl-pyrrolidone-containing compounds can be used as compatibilizers for plastic compositions; the compatibilizers attach themselves to the interface between the polymers involved, or penetrate into the polymers, thereby improving the adhesion between the polymers and enhancing mechanical properties.
5-Methyl-N-pyrrolidones can also be used as compatibilizers in the refrigeration and air conditioning industries. Transitioning from chlorofluorocarbon to hydrofluorocarbon refrigerants has necessitated the use of a new class of lubricants due to immiscibility with conventional lubricants such as mineral oil, poly xcex1-olefin and alkylbenzene. However the new class of lubricants is expensive and also very hygroscopic. Absorption of water leads to acid formation and corrosion of the refrigeration system, as well as the formation of sludges. The lack of solubility of the hydrofluorocarbons in the conventional lubricants results in a highly viscous lubricant in the non-compressor zones, and results in insufficient lubricant return to the compressor. This can eventually result in a number of problems, including the compressor overheating and seizing and insufficient heat transfer in the refrigeration system. Compatibilizers solubilize the polar halogenated hydrocarbon refrigerant and the conventional non-polar lubricant in the non-compressor zones, which results in efficient return of lubricant to the compressor zone. Compatibilizers may include the 5-methyl-N-alkyl- and 5-methyl-N-cycloalkyl-2-pyrrolidones.
Pyrrolidones can also be used as fuel and lubricant additives. For example, N-alkyl-2-pyrrolidones can be used as detergents and dispersants in fuel additive compositions to keep valves, carburetors and injection systems clean, thereby improving the combustion characteristics and reducing deposits, thus reducing air polluting emissions. In addition, 5-methyl-N-methyl-2-pyrrolidone can be used to remove unsaturated hydrocarbons from raw lube distillates or deasphalted residual lube stocks to produce solvent-refined base oils as lubricants.
Methods for the preparation of cleaning, stripping, agrochemical and plastic formulations are well known to persons skilled in the art. Similarly, methods for the preparation of insect repellants, ink jet inks, protective formulations for paint, fuel additives and lubricants, refrigeration and air conditioning lubricants, and for dry cleaning are well known in the art. Pyrrolidones can act as solvents, surfactants, dispersants, detergents, emulsifiers, viscosity builders and complexing agents in these formulations. Appropriate pyrrolidones are selected based on standard screening procedures for product performance. Additional components, such as pharmaceutical or agrochemical active agents or colorants, may be added to specific formulations as the main functional component; the nature of the functional component or components would be determined by the specific use. Auxiliary components, which enhance or are critical to the efficacy of the formulation, may also be added. Auxiliary components may include solvents or cosolvents, thickeners, antioxidants, spreading agents, preservatives, adhesives, emulsifiers, defoamers, humectants, dispersants, surfactants, suitable carriers, matrix systems, delivery vehicles, fragrances, salts, esters, amides, alcohols, ethers, ketones, acids, bases, alkanes, silicone, evaporation modifiers, paraffins, aliphatic or aromatic hydrocarbons, chelating agents, gases for aerosols, propellants or for dry cleaning, oils and water. Appropriate auxiliary components for the uses described herein are known to persons skilled in the art.
The following examples are illustrative of the invention. Examples 1 to 49 are actual examples; Examples 50 to 55 are prophetic.